debiting my account 2 months later

In December i used my debit card to pay for something at computicket 2 months later they have debited my account intial payment was made when i swiped my card so how can they charge my bank again without notifying me this cannot be legal and capitec allows this.Why did computicket not tell me about this debit and who gave them permission to debit my account.i received an sms and balance went reduced . pathetic service